KR20020051961A - A method for refining high phosphurous steel in converter - Google Patents

Abstract

The present invention relates to the production of Gorin steel for use in containers or electrical steel sheets and the like; The purpose is to provide the Gorin Steel with a final P component of about 0.05 ~ 1.2% by simply improving the method of adding subsidiary materials in the steelmaking process.

The present invention for achieving the above object is a method for producing a Gorin steel containing 0.05 to 1.2% by weight of phosphorus, from the beginning of the drilling while the molten iron containing a carbon content of 4.0 to 4.8% by weight in a conventional pattern At the time of progressing up to 35%, light dolomite of less than 5kg is injected per ton of molten steel, and the slag temperature is maintained at a temperature of 1550 ~ 1750 ℃ at the time of progressing up to 35 ~ 70%, and after 70% of progression. The technical gist of the converter refining method of the Corinth Steel, which consists of adjusting the final target temperature of the molten steel by adding coolant to it, shall be considered.

Description

A METHOD FOR REFINING HIGH PHOSPHUROUS STEEL IN CONVERTER}

The present invention relates to the production of Gorin steel, which is used in containers or electrical steel, and more specifically, by simply improving the input method of secondary raw materials in the steelmaking process, the phosphorus (P) component of the Gorin steel for up to about 0.05 ~ 1.2% The method of refining converters.

The steelmaking industry consists of charter preliminary refining, converter refining, secondary refining, and continuous casting. Among them, in the converter refining operation, the main raw materials, molten iron and scrap are charged into the converter, and pure oxygen is injected through the lance. Carbon, silicon, manganese, phosphorus, and sulfur are removed by oxidation.

In conventional steel grades, the content of phosphorus in the impurity element is less than about 0.025% by weight, but in steel materials such as steel for containers or electrical steel sheets, the amount of phosphorus in steel is required to be about 0.05 to 1.2% by weight. Nevertheless, in the refining of such Corinthian steel, conventionally, phosphorus in molten steel is manufactured at 0.025% or less at the point of time, and then phosphorus concentration is adjusted by adding ferroalloy containing a large amount of phosphorus during the tapping.

As a representative example, the converter refining method of the conventional Gorin steel (additional steel), first put 30kg to 40kg / TS of the slag in the preparation stage for the preparation, and after coating (coating) while inclining the converter 15kg / TS for the protection of the furnace body is added, and the quicklime added to the initial stage of the blow (beginning of the blow-treatment 33 ~ 35%) is thoroughly recycled early and the iron oxides in the slag are kept high. As soon as the lance was softened by soft blowing to reduce the yield, the lance was then lowered to promote de-manganese so that the Songsan Jett hit the molten iron. Next, in the middle of the blow (33% to 67% of the blow) is decarburized vigorously generated a large amount of carbon monoxide, at this time it is necessary to thoroughly suppress the method so that iron oxide in the slag made in the early stage of the blow is not reduced by the carbon monoxide. This raises the lance height and decreases the amount of acid, which induces the slag goods thoroughly to increase the basicity and to suppress the scavenging, and the iron oxide (sintered ore) and quicklime were divided into 4 to 5 times by 2 kg / t. Then, at the end of the blow process (67% to completion), the decarburization period is almost over, and the decarburization rate gradually decreases, oxidizing iron and manganese in molten iron, and iron oxide (FeO) and manganese oxide (MnO) are formed in the slag. Oxygen potential in slag and molten iron rises, leading to delinquency and demanganese. At this time, in order to more actively promote the de-manganese so that the phosphate in the slag can be more stably present, the lance height was lowered at the time of blowing 70% to 75%, and the flow rate was increased to induce more stable behavior. In particular, in order to stabilize stably, the end point carbon is less than 0.05% by weight and the phosphorus concentration is 0.015 ~ 0.025% by weight. It was. During the tapping, the amount of Fe-P (alloy iron) is added to the ladle after calculation to the lower limit of the specification range of the phosphorus concentration of the target steel grade based on the end point content (0.015% to 0.025%).

However, in the prior art for obtaining the above-mentioned Corinth steel, many secondary raw materials (quick lime and fluorspar) are consumed in order to obtain a stable end phosphorus, thereby increasing the manufacturing cost, and increasing the amount of slag for recyclability. Not only is it the main cause of environmental pollution due to the occurrence, but the manufacturing cost is increased by the addition of ferro-alloy (Fe-P) in the ladle, and the natural porosity decreases by injecting ferro-alloy (Fe-P) into the ladle bottom. There are many problems such as poor quality due to oxygen washing in the performance, deterioration of molten steel due to segregation and inclusions caused by impurities in the ferroalloy (Fe-P). In particular, the slag basicity ((CaO wt%) / (SiO ₂ wt%)] is required to be lowered compared to the conventional 2-3 in order to manufacture the Gorin steel, but according to the conventional method, the initial slag basicity [(CaO weight %) / (SiO ₂ wt%)] When operating with a low base of 1.0 or less, large slipping phenomenon in which slag in the converter blows out of the furnace hole and spitting phenomenon of splashing of iron in the converter occurs. In the operation, the refining work was performed in the same way as the normal low-lining steel operation method, and the coping with the ferroalloy (Fe-P) during tapping was performed.

In order to solve the above problems, the present inventors have experimented with 100 ton converters based on the experience and theory of converter operation technology and proposed the present invention based on the results, and the present invention has a target phosphorus content of 0.05 to 1.2% by weight. The purpose of the present invention is to provide a method for refining the converter for raising the end phosphorus by improving the input method of subsidiary materials while maintaining the existing blowing pattern for the steel refining, which is required to the degree.

1 is an example of the blowing pattern of the comparative example and the invention example and the sub-material input method.

Figure 2 is a graph showing the behavior of phosphorus in molten iron according to the blowing time of the comparative example and the invention example.

Figure 3 is a graph showing the behavior of phosphorus with carbon at the end of the comparative example and the invention example.

In the present invention for achieving the above object in the method for producing a phosphorus content of Gorin steel containing 0.05 to 1.2% by weight,

The molten iron having a carbon content of 4.0% by weight or more was blown in a normal pattern, and at the time of starting the drilling from 35% of the molten iron to less than 5 kg per ton of molten steel,

At the time of blow progress up to 35 ~ 70%, the slag temperature is maintained at a temperature of 1550 ~ 1750 ℃, and

The present invention relates to a method for refining the converter of the Gorin Steel, which includes adjusting the final target temperature of the molten steel by injecting coolant at the end of 70% of the drilling process.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In general, converter refining focuses on how to remove and remove phosphorus in the slag side more stably. In the refining of the converter, the Tallinn reaction is expressed as in Equation 1, where the equilibrium constant K may be expressed as in Equation 1.

4 (CaO) + 2 [P] + 5 [O] = (4CaO · P ₂ O ₅ )

log K = 78.700 / T-33.42

Here, K is an equilibrium constant, K = a _4CaOP2O5 / a _CaO ⁴ · a _p ² · a _o ⁵ , T is the absolute temperature, a _i means the activity of the i component of molten iron and slag.

From Reaction Scheme 1 and Equation 1, it can be seen that in order to increase phosphorus in molten steel, a _p must be increased. As a method, the following conditions can be considered.

First, the initial input of slag is slag early to reduce CaO activity.

Second, it lowers the basicity and iron oxide concentration in the initial slag of blowing.

Third, by adjusting the transmittance strength to narrow the firing point area to lower the oxygen potential of molten iron and slag (Oxygen Potential), to suppress the slag movement.

Fourth, the reaction rate of manganese and carbon in the flue gas and molten iron is adjusted through proper control of the lance height and the amount of acid.

Fifth, the supply of CaO and FeO is suppressed so that P ₂ O ₅ on the slag side is moved to the molten steel side by an oxygen jet.

Enumerating the optimal method for implementing the above method will be able to use the following method.

1) Adjust the basicity to 1-2 based on the fact that quicklime and fluorspar are not added.

2) Eliminate the input of secondary raw materials in the middle of drilling and if the molten steel becomes hot at the end of the period, adjust the target temperature by adding coolant.

3) Leave fine adjustments to ferroalloy after finishing the finishing work and make fine adjustments based on the component analysis values during tapping.

To this end, in the present invention, basically, as in the conventional method, first, while using the existing blowing pattern in the state of coating the inner wall of the converter with slag, the input of secondary raw materials is suppressed as much as possible, and the [P] content in the final molten steel is 0.05% or more, preferably. Preferably it is controlled in the range of 0.05 to 1.2%.

First, in the converter slag coating, as in the conventional method, in the converter operation using molten iron and scrap metal, the slag that was operated last time is charged, and after charging the minor raw material, Kyungso Dolomite, the slab is slag on the inner wall of the furnace three to four times. It is necessary to coat. This furnace coating not only extends the life of the furnace body but also helps to ensure the cleanliness of molten steel in the manufacture of corinth steel. At this time, the amount of slag remaining in the last charge (Charge) is quantified according to the operating conditions. The important point is to apply some of the light dolomite in the converter slag coating to the converter slag coating, and after the start of the injection of the small amount of light dolomite remaining in the total required amount for the protection of the furnace body. For example, about 20 kg / T-S of light dolomite is added to the converter slag coating, and the rest is added at the beginning of the blow.

After the converter slag coating is performed in this way, the injection conditions of the subsidiary materials are controlled while blowing in the usual blowing pattern.

Specifically, the general blow pattern is divided into the initial stage (the beginning of the drilling to 35% of the time), the middle stage (35 to 70% of the time) and the last stage (the 70% to the end), the lance is raised to increase (soft blowing), in the middle of the lance to lower the lance hard (hard blowing), and at the end of the soft again. For example, such a conventional blowing pattern is disclosed in Korean Patent Laid-Open Publication No. 2000-42510.

In the present invention, while keeping the usual blow pattern as it is, when the ignition is started with the initial start of the blow, when added to the quicklime lime 5 ~ 10kg / TS, and light small dolomite 5kg or less / TS, after the middle period, all the subsidiary materials are added to the furnace After maintaining the slag at a high temperature without the end, it is characterized by obtaining only 0.05% by weight of phosphorus concentration in molten steel at the end of the converter by only adding coolant for the final target temperature correction.

In the present invention, to reduce the amount of quicklime as much as possible to initially lower the basicity of the slag, if the input of quicklime is less than 5kg / TS, the slope phenomenon is severe and if the 10kg or more / TS slag basicity is higher Steel production is difficult and undesirable.

In addition, the introduction of light dolomite plays a role in promoting composition of slag, increasing the MgO concentration in slag, suppressing erosion of refractory, and forming a composition that is detrimental to Tallinn. However, when the light dolomite is added in more than 5kg / T-S spitting phenomenon occurs is not preferable.

On the other hand, in the case of the present invention, after the middle stage of the blow, FeO and P ₂ O ₅ in the slag generated in the early stage to reduce the temperature of molten iron and slag to facilitate the reduction of slag to maintain a high phosphorus concentration in the slag do not put any auxiliary raw materials in the furnace. Do not. Specifically, to maintain the temperature of the slag itself at about 1550 ~ 1750 ℃.

In addition, during the final stage, the tapping target temperature is finally adjusted while maintaining the high temperature without introducing any subsidiary materials into the furnace as in the middle stage. Normally, the final target temperature is about 1670 ~ 1680 ℃ to maintain the temperature of the tapping, but if the temperature of the molten steel is higher than the target temperature to enter the coolant, if the temperature of the molten steel can be adjusted by putting the heat source material. As the coolant, hot briquette iron (HBI) containing about 80% or more iron is preferably added.

This refining method of the present invention can be applied to any molten iron produced in the blast furnace. Preferably, the molten iron is preferably a molten iron containing 4.0 to 4.8 wt% of carbon, 0.2 to 0.5 wt% of silicon, 0.2 to 0.4 wt% of manganese, and 0.095 to 0.125 wt% of phosphorus. However, when refining the Gorin steel using a molten iron having a Si content of 0.20% or less, it is preferable not to add quicklime in consideration of the basicity of slag.

As described above, according to the refining method of the present invention, while keeping the existing blowing pattern as it is, the input of less raw material is added, the suspended inclusions in the molten steel can be reduced to improve the cleanliness of the molten steel.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

EXAMPLE

After leaving about 3 tons of slag last operated in 100 ton capacity converter, 10kg / T of light and small dolomite was added and the slab was coated 3 times and 4 times to coat slag on the furnace wall. / t was charged into the furnace, and then, as main raw materials, scrap metal and molten iron (less than 15% of the total charge) were charged into the converter. The molten iron used at this time had a composition of 4.5% by weight of carbon, 0.2-0.5% by weight of silicon, 0.2-0.4% by weight of manganese, and 0.095% by weight to 0.125% by weight of phosphorus. In this way, after the furnace was established, the lance was lowered and blown as shown in FIG. 1. That is, the blowing pattern from the start of the blow to the end of the blow was the same in both the conventional method and the present invention. However, the method of adding the subsidiary materials was carried out in the following two ways at the same time as the start of blowing. At this time, the component analysis values for the various auxiliary ingredients introduced in the present embodiment are summarized in Table 1.

division Chemical composition (% by weight) CaO MgO T. Fe SiO ₂ Al ₂ O ₃ C CaF ₂ S quicklime 92.5 2.2 0.39 0.92 0.30 - - - Dolomite 56.16 38.8 0.6 1.40 0.51 - - - fluorite - - - 13.54 - - 83.86 - Sintered ore 8.42 1.24 48.29 4.54 1.56 2.60 - 0.034

(Conventional example)

As shown in Figure 2 at the start of the blow, irrespective of the concentration of molten silicon, 5 to 10 kg / TS of quicklime and 3 to 10 kg / TS of sintered ore were added. / TS, sintered ore 3 ~ 10kg / TS was interlocked and at the same time divided into small and small dolomite 1-5kg / TS, and at the end of the blow (70% ~ finishing time), quicklime 2 ~ 3kg / TS, sintered ore 3 ~ 10kg / TS, Gyeongso Dolomite 1 ~ 3kg / TS was input.

(Invention example)

At the start of the blow, 10 kg / T-S of quicklime and 5 kg / T-S of light calcinal dolomite were added, and the temperature of the slag was maintained at 1700 ° C. without adding any subsidiary materials from the middle of blowing. Thereafter, briquettes containing 80% or more of iron was added for temperature correction, and the target temperature of the final molten steel was maintained at 1680 ° C.

Table 2 summarizes the results of refining and analyzing the molten steel at the end of the blow (finishing point) by performing the refining operation 10 times in each of the blow patterns of the conventional example and the invention example.

division Molten steel component (weight%) at the end of blow C Mn P Conventional Example 1 0.039 0.07 0.015 Conventional Example 2 0.030 0.05 0.021 Conventional Example 3 0.042 0.10 0.020 Conventional Example 4 0.035 0.06 0.019 Conventional Example 5 0.034 0.07 0.020 Conventional Example 6 0.035 0.06 0.018 Conventional Example 7 0.055 0.09 0.017 Conventional Example 8 0.040 0.09 0.016 Conventional Example 9 0.071 0.07 0.017 Conventional Example 10 0.029 0.06 0.017 Inventive Example 1 0.055 0.17 0.085 Inventive Example 2 0.065 0.18 0.070 Inventive Example 3 0.061 0.19 0.084 Inventive Example 4 0.045 0.17 0.077 Inventive Example 5 0.057 0.16 0.080 Inventive Example 6 0.070 0.17 0.075 Inventive Example 7 0.065 0.22 0.077 Inventive Example 8 0.050 0.19 0.080 Inventive Example 9 0.066 0.23 0.095 Inventive Example 10 0.047 0.17 0.089

As shown in Table 2, after the end of the analysis, as a result of analysis, the conventional examples (1 to 10) were low as 0.029 to 0.071% by weight of carbon and 0.05 to 0.10% by weight of manganese, and the distribution of phosphorus was lower than 0.020%.

On the other hand, in the case of the invention examples (1 ~ 10), the carbon concentration was relatively high as 0.047 ~ 0.07% by weight, manganese was high as 0.17 ~ 0.23% by weight and phosphorus was high as 0.07 ~ 0.089% by weight.

As a result, according to the present invention it can be seen that the manganese is 0.1% by weight higher than the conventional, phosphorus can be higher than 0.05% by weight.

On the other hand, Figure 2 shows the behavior of phosphorus in molten iron during the blowing in the above embodiment. In the case of the conventional example, the concentration of phosphorus in molten iron decreases rapidly from the start of the blow to 20% of the blow time, but there is almost no change thereafter, and at the end, the phosphorus concentration is 0.02% by weight or less.

On the other hand, the present invention shows that the concentration of phosphorus decreases from the start of the scavenging to 20%, but the decrease is very small compared with the conventional case, and then the concentration of phosphorus in the molten iron increases to 0.1% by weight until 60% of the scavenging time. After 60%, there was a tendency to decrease slightly, but the extent of the decrease was almost suppressed, indicating that a high phosphorus concentration was obtained at 0.085% by weight at the time of termination.

In addition, Fig. 3 schematically shows the correlation between the end point carbon and the end point phosphorus concentration at the blowing end point. As can be seen in FIG. 3, in the case of the conventional example, 0.025 to 0.05 wt% of end point carbon and 0.015 to 0.025 wt% of phosphorus concentration were obtained. In the present invention, 0.045 to 0.07 wt% of end point carbon was obtained. Was obtained at 0.055% to 0.080% by weight.

On the other hand, if the target phosphorus concentration of the target steel grade is to produce a Gorin steel of about 0.1 to 1.2% by weight, based on the above Table 2 and Figure 3 by inputting ferroalloy (Fe-P) to the phosphorus content of the final steel What is necessary is just to adjust to 0.10 to 1.2 weight%.

As described above, by inducing high end carbon and phosphorus concentration at the end of the work by improving the method of inputting the sub-materials during the converter converter, the working time is shortened and the slag generation amount is reduced, thereby improving workability during drilling, It is possible to reduce the ferroalloy (phosphorus, manganese) in the field, and in particular, by reducing the amount of deoxidizer input during tapping, the source of inclusions in the steel is reduced, so the effect of quality improvement is great.

Claims (2)

In the production method of Gorin steel containing phosphorus content of 0.05 to 1.2% by weight, While melting molten iron containing 4.0 to 4.8% by weight of carbon in a normal pattern, at the time of starting the drilling from 35% of the molten iron to less than 5 kg per tonne of molten steel, At the time of blow progress up to 35 ~ 70%, the slag temperature is maintained at a temperature of 1550 ~ 1750 ℃, and The method of refining the converter of Gorin Steel, comprising: adjusting the final target temperature of the molten steel by injecting a coolant at the end of 70% of the drilling process. The method of claim 1, When the Si content of the molten iron is 0.2 ~ 0.5%, the converter refining method of the Gorin steel, characterized in that 5 ~ 10kg of quicklime is added to the beginning of the blow.